The present invention relates to a color ink jet recording method and apparatus which supplies a plurality of ink ejection heads with ink of different colors so as to selectively print out dots on a sheet in response to input color signals. More particularly, the present invention relates to a color ink jet recording method for reproducing on a sheet a halftone color image by regulating the density of dots to be formed on a sheet.
Prior art color ink jet recording methods include one disclosed in Japanese Unexamined Patent Publication (Kokai) No. 56-146361. In this prior art method, print dot patterns corresponding to color densities (dot patterns in a matrix or pixel having a predetermined number of elements) are assigned to each color, so that specific one of the patterns may be selected to print out dots as specified by color density instruction.
With the method described above, it is possible to record color data with gradation from a low density to a medium density and monochromatic data over the entire gradation. However, regarding color ink jet recording which prints out dots of two or more colors in a same matrix, if dots zero to k (k being the number of elements in the matrix) are simply printed out in response to an input level of each color, the dots will join each other, blur or even flow on the sheet when data is reproduced to a relatively high density. For example, when all the three colors, yellow, magenta and cyan, are at the highest level, ink of the three different colors will be printed out one upon another. In practice, the flow or the blur of ink may be overcome by replacing at least part of yellow (Y), magenta (M) and cyan (C) dots by black (BK) dots. However, when yellow (Y) and magenta (M) are at the highest level for example, ink of the two colors will become superposed in each element of the matrix resulting in the flow or the blur of the ink.